Osmosis as passive water movement across membranes

Steps:

• Identify the direction: molecules moving out of the cell through the membrane.
• Recall transport types: passive (no energy) vs. active; simple vs. facilitated.
• Match to osmosis: net movement of water from high to low concentration.
• Eliminate non-water or energy-requiring processes.

Why C is correct:

• Osmosis is the diffusion of water molecules across a semi-permeable membrane from higher to lower water potential, matching outward movement in hypertonic conditions.

Why the others are wrong:

• A: Exocytosis uses vesicles and energy to expel large molecules, not simple membrane passage.
• B: Facilitated diffusion requires carrier proteins for specific solutes, not general outward flow.
• D: Diffusion is for any solutes without water specificity or osmotic gradient.

Final answer: C